For basic types, you can also use packed encoding to reduce the space
required; just add [packed=true] to a "repeated" element.

Marc

On Oct 8, 4:46 pm, Constantinos Michael <constanti...@google.com>
wrote:
> On Thu, Oct 8, 2009 at 5:35 PM, sergei175 <sergei...@googlemail.com> wrote:
>
> >  Hi,
>
> >  I've looked at protocol buffers, and I've noted that there is no
> > support for arrays
> >  of values (double, integers). This is a significant drawback, for
> > example
> >  JSOM, HDF5 etc they all have this.
>
> Have you looked at "repeated" fields? You can define one like so:
>
> repeated double my_number = 1;
>
>
>
>
>
> >  One post suggested  that one should put an array  as one single
> > string in a field
> >  I've did this, and the performance  was very bad in Java and very
> > memory consuming
> >  (compare to the standard Java serialization).
> >  I've wrote 500 times the same array (10,000 double numbers ), and
> > after the array 500,
> >  my computer was out of memory,
>
> >  Secondly, all tutorials suggest that the file should be written at
> > once, i.e. at the end
> >  of the program, when the messages
> >  are filled. I want to write data to the disk in several steps. say I
> > want to write one record first (say, one array),
> >  then I want to append data to the existing file, and so on, this way
> > I will not need
> >  to keep all records in the computer memory. The merge mechanism
> > shown in the tutorial
> >  seems parses the old file
> >  first, and then add new record, and write a new file.
>
> >  Do I understand this correctly? If yes, then the protocol  buffers is
> > not too good for large data volumes,
> >  especially with numerical arrays
>
> >  best wishes, Sergei
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